In spinning mills, it is usual to lay out several large spinning machines parallel to each other, whereby the individual spinning machines have a plurality of spinning units, for instance 20 to 200 units, on each side receiving the fiber strands to be spinned from cans which are arranged standing on the bottom, underneath the spinning units. As a rule, two cans are provided for each spinning unit, whereby from one of the cans the fiber strand is taken up for spinning, and the other can is either a full spare can or an already empty one. As a rule, the fiber strand is taken up from the can which stands in the front, in the first row. As soon as this is empty, it is replaced by the full can standing in the second row. The supply, exchange and monitoring of the cans at the spinning units are relatively time-consuming and cumbersome.
From the German open application DE OS No. 26 46 313 and installation of the afore-described kind is known which makes possible the automatic exchange of cans at the spinning units of a spinning machine. The conveying installation used is an overhead conveyor whose tracks are arranged at the spinning machine. The conveyor truck comprises two arms, of which one arm serves for the receiving of an empty can from the spinning unit and its evacuation, while the other arm serves for the feeding and delivery of full cans to the spinning unit. In order to be able to manipulate the cans arranged one after the other in rows at a spinning unit, three or four cans of neighboring spinning units are arranged on a turn table, which is actuatable from the devices of the conveyor truck. This apparatus has the disadvantage that all spinning units have to be equipped with such complicated turntables, whereby it becomes expensive and complicated to operate, especially since the mounting of such a conveying installation at already existing spinning machines is not possible for many reasons, and in any case would be complicated and expensive.